Description To 1" (2.2 cm). Tiny, but stout and deep-bodied; female deeper-bodied than male. Fins large and rounded with dark edges; dorsal and anal fins far back on body. Females and juveniles generally yellowish to yellow-brown; males silvery with iridescent blue highlights.

Endangered Status The Devils Hole Pupfish is on the U.S. Endangered Species List. It is classified as endangered throughout its range in Nevada. Most of the 13 species of Cyprinodon in the United States are restricted to springs or streams in the deserts of Texas, New Mexico, Arizona, Nevada, and California. Several species are endangered, mainly because of water-management practices, including the siphoning of their water for crop irrigation, desert development, and the introduction of exotic fishes. The Devils Hole Pupfish was the focal point of a famous U.S. Supreme Court water rights case in the 1970s, brought by the federal government against a farming concern that was pumping the water from wells associated with Devils Hole. These fish breed on ledges just a few inches below the water surface, and continued pumping would have lowered the water level to below the ledges, thus exposing and exterminating the fish. The campaign for the pupfish gained national attention and helped galvanize the environmental movement. The courts decided in favor of the fish, and after many years of bureaucratic wrangling, the Ash Meadows National Wildlife Refuge was established to protect the unique ecosystem of Devils Hole and the pupfish and other creatures that live in it.